Distributed parameters delay line,on folded support

ABSTRACT

A distributed parameter electromagnetic delay line is obtained by superimposing insulating thin foldable substrates carrying conductive patterns, which form, when folded in accordionlike fashion, a helicoidal winding composed of a plurality of turns interleaved with grounded conducting areas. As an alternate construction, a single insulating substrate carrying conductive patterns on both sides may be used.

United States Patent Inventor Georges Kassabgi Pregnana Milanese, Milano, Italy Appl. No. 779,428 Filed Nov. 27, 1968 Patented Sept. 28, 1971 Assignee General Electric Information Systems,

S.p.A. Caluso, T urin, Italy Priority Nov. 27, 1967 Italy 23,162A/67 DISTRIBUTED PARAMETERS DELAY LINE, ON FOLDED SUPPORT 14 Claims, 27 Drawing Figs.

U.S. Cl 333/31 R, 333/70 S, 333/84 R H03h 7/32 Field of Search 333/31 84,

84 M, 70 S; 3l5/3.6 X

[56] References Cited UNITED STATES PATENTS 2,014,524 9/1935 Franz 333/705 3,327,248 6/1967 Johnson 333/31 Primary Examiner-H. K. Saalbach Assistant Examiner-Saxfield Chatmon, Jr. Attorneys-George V. Eltgroth and Joseph B. Fonnan ABSTRACT: A distributed parameter electromagnetic delay line is obtained by superimposing insulating thin foldable substrates carrying conductive patterns, which form, when folded in accordionlike fashion, a helicoidal winding composed of a plurality of turns interleaved with grounded conducting areas. As an alternate construction, a single insulating substrate carrying conductive patterns on both sides may be used.

PATENTED SEP28 1971 SHEEI 2 BF 5 FIG. 6

INVIz'N'l'UR.

GEORGES KASSA as! A T TORNEY {MEN-15930281911 I IN Vlz'N TOR.

7 0mm: usual A T TORNE Y FIG. 79

FIG. 76

F1616 FIG. 17

FIG. 27

IN Vlz'N'l'UR.

GEORGES KASSABGI ATTORNEY PATENT Eusirzsmn 3,609,600 snms urs FIG. 27

INVEN'I'OR.

csonass KASSABGI ATTORNEY DISTRIBUTED PARAMETERS DELAY LINE, ON FOLDED SUPPORT The present invention relates to distributed parameter delay lines.

U.S. Pat. No. 3,543,194 filed Oct. 24, 1968 by the same applicant disclosed electromagnetic delay lines built by alternatively stacking insulating and conductive flat elements, which are electrically connected together either by soldered or by pressure contacts.

The present application discloses an electromagnetic distributed parameter delay line formed with continuous conductors, requiring neither soldered nor pressure connections between elements. This is obtained through the use of well known printed circuit techniques, to provide conductive patterns on one or both sides of a dielectric substrate.

One type of delay line, formed according to the invention, comprises a first and a second thin flat insulating substrate of foldable material. A continuous conductor of suitable shape is provided on one side of the first substrate and conductive interconnected areas are provided on one side of the second substrate. Both substrates are placed in contact with one another, the side of the first support carrying the continuous conductor being in contact with the side of the second substrate not carrying the conductive areas. Both substrates are folded along predisposed suitable folding lines in a manner such that, when folded, the continuous conductor on the first support forms a substantially helicoidal winding, therefore exhibiting a well defined inductance, the conductive areas of the second substrate being interleaved between the single turns of the said helicoidal winding. The capacity between these conductive areas, which are connected to ground, or any suitable reference voltage, and the winding, provides the distributed capacity of the line.

According to an alternative form of the invention, the delay lines comprise a single insulating foldable thin substrate, carrying a continuous conductor on one side and properly shaped conductive regions on the opposite side. By folding the substrate along predisposed suitable folding lines the continuous conductor forms a helicoidal winding, the conductive regions of the opposite side of the substrate being interleaved between single turns and insulated therefrom.

The delay lines formed according to the invention are very compact, small and adapted to be mounted on standard printed circuit cards, like any other electronic component.

These and other features and advantages of the present invention will be better understood from the following detailed description of a number of preferred embodiments, with reference to the accompanying drawings in which:

FIG. 1 shows two insulating strips supporting suitably shaped conductive patterns.

FIG. 2 shows the insulating strip of FIG. 1 when folded and interleaved.

FIG. 3 shows the final appearance of a delay line built according to the invention.

FIG. 4 and 5 represents two suitable shapes of the continuous conductor.

FIGS. 6, 7, 8 and 9 show alternative patterns of the conductive grounded areas.

FIG. 10 represents a delay line provided with intermediate taps.

FIG. 11 is an exploded view of a delay line provided with adjustable delay feature.

FIG. 12 shows the pattern of continuous. conductors which are part of an assembly of series connected delay lines.

FIG. 13 shows the final aspect of such delay lines assembly.

FIG. I4 shows another pattern which provides the same effect.

FIG. 15 shows the final aspect of the corresponding assembly.

FIGS. 16 and 17 show the opposite faces of a single insulating strip having conductive pattern on both faces.

FIGS. 18 and 19 show the folded line of FIG. 16 and 17 as viewed from two different directions.

FIG. 20 shows a possible pattern of a continuous conductor on a strip having double width.

FIG. 21 shows the manner of folding said strip to obtain a winding.

FIGS. 22, 23 and 24 show three possible patterns of the continuous conductor on one face of the insulating strips.

FIGS. 25, 26 and 27. show respectively the manner for folding said strips.

Referring now to FIG. 1 a delay line constructed according to the invention, is formed by assembling two continuous insulating strips, 1 and 2, made from thin dielectric and easily foldable material subject to low dielectric losses, such as, for example, polytetrafluoroethylene, more commonly identified by the trade name Teflon or other suitable similar material.

The thickness of the support, for example, may be 50 microns.

Each one of these strips may be considered as divided in adjacent regions, alternately identified by reference letters a and 11. These regions are bounded by the edges of the strips and by folding lines, perpendicular to the edges, alternately identified by reference letters c and d. g

A continuous conductor 3, in the form of a narrow strip, is carried on a face of strip 1. It may be obtained, for example, by pressure rolling a thin metallic layer, for example copper, on a surface of the insulating support, and thereafter removing predetermined portions of said layer by photoetching, according to processes which are well known in the printed circuit art.

The pattern of the continuous conductor 3, which extends along the entire length of the insulating strip I, substantially exhibits a succession of curved segments 4 and 5, having their convexity alternately oriented towards the opposite edges of the strip and alternately contained in regions a and b.

A plurality of grounded areas 6 is obtained in the same manner on one side of strip 2. These grounded areas may, for

' example, occupy only regions a, and be shaped in difi'erent forms, provided they do not form closed loops when the substrate is folded, and do not comprise continuous conductive areas of relevant extension, which may become the source of eddy currents. The conductive areas 6 are connected together by rectilinear stretches 7 of the conductor, traversing regions b.

As shown in FIG. 2, strips 1 and 2 are alternately folded in an opposite sense along lines 0 and a, and the folds are interleaved as shown in FIG. 2. The curved segments 4 and 5 of the conductor 3 then form a complete turn, but are insulated from one another, except for the stretch traversing lines d, by the double thickness of the folded insulating substrate 1, whereas the insulation between consecutive turns is provided by the double thickness of the folded interposed insulating substrate 2. The turns are serially connected by lengths of conductor traversing lines 0. Grounded areas 6 are therefore interleaved between consecutive turns, being insulated therefrom by the thickness of the substrate 2.

A delay line is thus obtained, having a substantially helicoidal winding showing a well defined inductance, and a distributed capacity toward ground, or any suitable reference voltage.

FIG. 3 shows a final version of the delay line, when contained in a suitable casing, and provided with two terminal pins 8 and 9, connected to the ends of the continuous conductor, and a ground pin 10, connected to the grounded areas.

The shape of the curved segments which form the turns of the winding may be different, being controlled by different conditions and requirements.

FIG. 4 shows how to obtain square turns, different from the one illustrated by FIG. 1, and FIG. 5 shows a suitable shape of the continuous conductor 5 for obtaining circular turns.

Likewise, the grounded areas may be differently shaped. They may occupy regions a only, either as a comblike pattern as shown in FIG. I, or by shapes similar to the shape of the turns they face, as shown in FIG. 6 for circular turns, and in FIG. 7 for square turns. They may also occupy opposite halves of regions a and b alternately, in a manner such that when the strips are folded and interleaved, the resulting grounded areas have a shape similar to the one of the facing turns, as shown in FIG. 8, wherein the dotted lines in region a indicate the position occupied by the conductive areas of region b, when the strip is folded. In the design of such areas care must be taken that, when folded, closed loops are not formed.

In FIG. 9 the grounded areas are obtained by means of a continuous conductor which forms open turns serially connected but wound alternately in opposite sense, when the strip is folded along the dotted lines, so that a noninductive winding results. To avoid closed loops, the portions of the conductor indicated by reference letter m in FIG. 9 must be separated by a small distance from the center line of the strip. As indicated in U.S. Pat. No., 3,543,l94 it may be convenient for the grounded regions not to completely shield consecutive turns,

leaving a predetermined capacity between some of the consecutive turns, to compensate for the changes in inductance at different frequencies. This capacitive coupling between turns is obtained by proper design of the conductive areas, for example, as shown in FIGS. 6, 7 and 9, wherein the width of the gap may be determined so as to obtain the required capacity between consecutive turns.

A delay line constructed as described, having a volume of 1 cubic centimeter, may exhibit a delay time ranging from approximately to nanoseconds, and having a maximum operating frequency of about 60-80 MI-Iz.

It is possible to provide intermediate taps, by interposing, in predetermined turns of the winding, thin connecting metal tongues contacting the conductor and projecting outside the line, as shown in FIG. 10.

Continuous variability of the delay time may be obtained, as shown in FIG. 1 l by providing means for subjecting the folded line to variable compression, thus changing the capacity of the single turns toward ground. FIG. 11 shows a screw 13 of insulating material, provided with a square head 14 and a threaded stem 15, inserted in a central aperture traversing the folded line. An insulating plate is superposed on the line, and a threaded nut 18 is screwed onto the stem 15, thus subjecting the line to an adjustable compression. As a consequence, the distance between winding turns is changed slightly and the capacitive coupling between turns and grounded areas changes correspondingly.

FIGS. 12 and 13 show the manner for obtaining an assembly of delay lines, to obtain a total delay time which is a multiple of the elementary line, without reducing the maximum operating frequency. As is known, this may be obtained by serially connecting elementary delay lines which are not inductively coupled together.

FIG. 12 shows a preferred form of continuous conductor pattern 19, located on a face of the insulating foldable substrate 20, of a width, as to contain several elementary strips like the strip of FIG. 1. A plurality of windings, series connected, and placed side by side are obtained by folding the substrate alternately in opposite sense along lines I and f. A folded substrate, carrying a corresponding plurality of grounded areas, is then interleaved between the folds of the first substrate. FIG. 13 shows the folded multiple delay line. Reference number 21 indicates the continuous conductor forming the turns of the windings. Reference number 22 indicates the grounded areas, partially cut away to show the underlying turns. FIG. 14 indicates an alternate pattern of a continuous conductor, suitable for obtaining a greater number of elementary delay lines serially connected, when the substrate is folded alternately in opposite direction around lines g and h, and a second substrate, not shown, carrying the grounded areas is interleaved therein.

If cylindrical bores are pierced through the whole assembly, as shown in FIG. 15, cylindrical cores 25 of ferromagnetic low loss material may be inserted into said bores, thus increasing the inductance of the line and the delay time, which may reach about ten microseconds, or more.

A modified form of the invention makes use of a single insulating strip, having on one face the continuous conductor originating the winding, and on the other the grounded areas.

No difficulty arises in the use of the grounded areas, which may be shaped as previously described. As far as the turns of the winding are concerned, attention must be given to the fact that folding the substrate, the conductive pattern of regions a and b may come in contact with one another thus forming closed loops.

FIG. 16 represents side 26 of an insulated strip, which supports the continuous conductor 27 forming the winding. The strip is divided into regions a and b by folding lines c and :1. Folding the uppermost region a over the following region b, a rectangular turn is formed as shown by the dotted lines drawn on region b. This turn is open, due to the fact that a small gap z exists between the terminal points 27 and 28 of the turn. The terminal point 28 is connected to the point 29 of the next turn by a short stretch of conductor crossing the folding line d. To avoid the closure of the turn, the terminal point 30 of this turn is shifted to the right by a small quantity with respect to point 29, to provide the small gap 2 between terminal points of the turn. The same occurs for the following turns, causing a progressive shifting of terminal points to the right, until the terminal point 31 of a turn reaches the extreme right position. Then the conductor is brought back to the left edge of the strip by means of a straight stretch, 32, normal to the folding lines and extending through two regions a and b, and a stretch 33, parallel to the folding line d. This portion 33 of the continuous conductor faces portion 35, but is insulated therefrom by the thickness of regions a and b immediately preceding it.

FIG. 17 shows a preferred shape of the grounded areas located on the opposite face of the same insulating strip, as viewed through the substrate. The relative positions of the continuous conductor 27 and of the grounded areas may be realized by superimposing FIG. 16 upon FIG. 17 by means of a parallel translation. FIG. 18 and FIG. 19 are two views, from different directions, of a delay line obtained by folding the described strip. The delay line is represented partially unfolded in order to show the conductor and the areas on regions a and b.

It is clear that the varied shapes and construction arrangements described with reference to the above-described embodiment, which involved two separate substrates, one for the continuous conductor and one for the grounded regions, are generally applicable to the second embodiment involving one substrate only, carrying on one face the continuous conductor and on the other the grounded areas; therefore it is not necessary to describe in detail the forms of application of the varied shapes and construction arrangements for the said second embodiment.

FIG. 20 shows an embodiment wherein the continuous conductor is carried on a double width strip. Every single turn is obtained by first folding the strip along the central line X-X, and then along the transverse folding lines, as shown in FIG. 21. The stretches of the continuous conductor, which cross the central line are suitable shifted in the downward direction in order to avoid contact between them.

The same effect, of avoiding the contact between connecting stretches of conductor across the folding lines may be attained by using folding lines alternately inclined first in one direction and then in the other with respect to the edges of the strip.

By reason of the inclination of these lines, each of the turns obtained by folding the substrate are rotated a definite degree with respect to the adjacent ones, so that the connecting lengths are shifted and do not come in contact with one another, as shown in FIG. 25.

Other alternate forms based on the same idea are shown in FIG. 23 and FIG. 24, in which the oblique folding lines result in triangular regions. Each one of these regions contains a one-third part of a complete turn. windings having triangular or circular turns may be obtained, according to the shape of the continuous conductor, by alternately-folding the strip in opposite direction along the oblique folding lines. (FIG. 26 and 27). The resulting assembly has the shape of a triangular prism. The connections traversing the folding lines are reciprocally insulated.

In FIGS. 21 to 27 the grounded areas are not represented for reasons of clearness, as from the preceding descriptions it is easy to understand how they may be formed and shaped.

It is believed useful to indicate that the described technique, may be used for fabricating inductors, if no grounded areas are provided, or for fabricating transformers, by juxtaposing and interleaving two or more windings and providing no grounded areas.

What is claimed is:

1. An electromagnetic delay line comprising:

a thin flat elongated insulating substrate,

a continuous conductor on one surface thereof forming a series of repetitive patterns,

said substrate being folded in alternate directions relative to the plane thereof along lines transverse to and spaced apart along the length of said substrate, said conductor forming a respective segment of the turn of a coil in each one of a set of successive regions along said substrate, each of said regions comprising the portions of said substrate between adjacent ones of said transverse lines, wherein all of said segments in each one of said sets form a complete coil turn, wherein all of said segments of said substrate form a multiturn coil,

a plurality of grounded areas on the other surface thereof,

a first terminal connected to one end of said conductor,

a second terminal connected to the other end of said conductor,

means for connecting to said grounded areas,

means for adjusting the spacing between adjacent regions of said substrate,

said means for adjusting the spacing between regions comprising an aperture through each region of said substrate, a tensioning member including a threaded portion at one extremity thereof extending through said aperture and having the other extremity thereof in pressure contact with one end of the folded assembly and threaded means riding on said threaded portion of said tensioning member for adjusting the tension between the ends of the folded assembly.

2. An electromagnetic delay line comprising:

a thin flat elongated insulating substrate,

a continuous conductor on one surface thereof forming a series of repetitive patterns,

said substrate being folded in alternate direction relative to the plane thereof along lines transverse to and spaced apart along the length of said substrate, said conductor forming a respective segment of the turn of a coil in each one of a set of successive regions along said substrate, each of said regions comprising the portion of said substrate between adjacent ones of said transverse lines, wherein all of said segments 'in each one of said sets form a complete coil turn, wherein all of said segments of said substrate form a multiturn coil, 5

a first terminal connected to one end of said conductor and a second terminal connected to the other end of said conductor,

a plurality of conductive areas noninductively interconnected, capacitively coupled to, insulated from and-interleaved between facing pairs of said regions, and

a third terminal connected to said plurality of conductive areas.

3. A electromagnetic delay line as defined in claim 1 and including taps at predetermined turn positions of said coil.

4. An electromagnetic delay line as defined in claim 2 including means for adjusting the spacing between adjacent re gions of said substrate.

5. An electromagnetic delay line as defined in claim 4 said means for adjusting the spacing between regions comprising an aperture through each region of said substrate, a tensioning member including a threaded portion at one extremity thereof extending through said aperture and having the other extremity thereof in pressure contact with one end of the folded assembly and threaded means riding on said threaded portion of said tensioning member for ad usting the tension between the ends of the said fan-fold assembly.

6. An electromagnetic delay line as defined in claim 5 and wherein said tensioning member is of a material having magnetic properties.

7. An electromagnetic delay line comprising:

a thin flat elongated insulating substrate,

a continuous conductor on one surface thereof forming a series of repetitive patterns,

said substrate being adapted to be folded in alternate directions relative to the plane thereof along lines transverse to and spaced apart along the length of said substrate, said conductor forming a respective segment of the turn of a coil in each one of a set of successive regions along said substrate, each of said regions comprising the portion of said substrate between adjacent ones of said transverse lines, wherein all of said segments in each one of said sets form a complete coil turn, wherein all of said segments of said substrate form a multiturn coil, and

a plurality of grounded areas on the other surface thereof.

8. The electromagnetic delay line formed by folding the substrate of claim 7 in alternate directions relative to the plane thereof along said transverse lines.

9. The electromagnetic delay line of claim 8 further including a first tenninal connected to one end of said conductor, a second terminal connected to the other end of said conductor, and means for connecting to said grounded areas.

10. An electromagnetic delay line as defined in claim 9 and including taps at predetermined turn positions of said coil.

11. An electromagnetic delay line as defined in claim 9 including means for adjusting the spacing between adjacent regions of said substrate. v

12. An electromagnetic delay line as defined in claim 1 and wherein said tensioning member is of a material having magnetic properties.

13. An electromagnetic delay line comprising a first nonconductive substrate, said substrate having a first repetitive plurality of conductive segments thereon forming a continuous conductor, a second nonconductive substrate having a second repetitive plurality of conductive areas thereon forming a continuous conductor, said second substrate being superimposed'in suitable relationship on said first substrate, said first and second substrate being plicated in accordionlike fashion along selected plication lines, whereby said first plurality forms a multiturn coil of serially connected turns having at least first and second terminals and said second plurality forms a set of parallel connected ground planes interleaved between said turns and insulated therefrom.

14. An electromagnetic delay line comprising a nonconductive two-sided substrate, said substrate having a first repetitive plurality of conductive segments being serially connected forming a first continuous conductor on one side thereof and a second repetitive plurality of conductive areas being parallel connected forming a second continuous conductor on the other side thereof in predetermined relationship with said first conductor, said first and second conductors being insulated from one another by said substrate said substrate being plicated in accordionlike fashion along selected plication lines, whereby said first plurality forms a multiturn coil of serially connected turns having at least first and second terminals and said second plurality forms a set of parallel connected ground planes interleaved between said turns and insulated therefrom.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pat t N 3 Dated September 28 1971 Georges Kassabgi It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

"said fan-fold" should read folded Column 6, line 7,

accordion-like line 63, "accordionlike" should read Signed and sealed this 29th day of August 1972.

(SEAL) Attest:

RGBERT GOTTSCHALK EDWARD M.FLETCHER,JR.

Commissioner of Patents Attesting Officer FORM PO-IOSO (10-69) USCOMM-DC 50376-1 69 U S GDVERNMENY PRINTING OFFICE I569 O-366334 

1. An electromagnetic delay line comprising: a thin flat elongated insulating substrate, a continuous conductor on one surface thereof forming a series of repetitive patterns, said substrate being folded in alternate directions relative to the plane thereof along lines transverse to and spaced apart along the length of said substrate, said conductor forming a respective segment of the turn of a coil in each one of a set of successive regions along said substrate, each of said regions comprising the portions of said substrate between adjacent ones of said transverse lines, wherein all of said segments in each one of said sets form a complete coil turn, wherein all of said segments of said substrate form a multiturn coil, a plurality of grounded areas on the other surface thereof, a first terminal connected to one end of said conductor, a second terminal connected to the other end of said conductor, means for connecting to said grounded areas, means for adjusting the spacing between adjacent regions of said substrate, said means for adjusting the spacing between regions comprising an aperture through each region of said substrate, a tensioning member including a threaded portion at one extremity thereof extending through said aperture and having the other extremity thereof in pressure contact with one end of the folded assembly and threaded means riding on said threaded portion of said tensioning member for adjusting the tension between the ends of the folded assembly.
 2. An electromagnetic delay line comprising: a thin flat elongated insulating substrate, a continuous conductor on one surface thereof forming a series of repetitive patterns, said substrate being folded in alternate direction relative to the plAne thereof along lines transverse to and spaced apart along the length of said substrate, said conductor forming a respective segment of the turn of a coil in each one of a set of successive regions along said substrate, each of said regions comprising the portion of said substrate between adjacent ones of said transverse lines, wherein all of said segments in each one of said sets form a complete coil turn, wherein all of said segments of said substrate form a multiturn coil, a first terminal connected to one end of said conductor and a second terminal connected to the other end of said conductor, a plurality of conductive areas noninductively interconnected, capacitively coupled to, insulated from and interleaved between facing pairs of said regions, and a third terminal connected to said plurality of conductive areas.
 3. A electromagnetic delay line as defined in claim 1 and including taps at predetermined turn positions of said coil.
 4. An electromagnetic delay line as defined in claim 2 including means for adjusting the spacing between adjacent regions of said substrate.
 5. An electromagnetic delay line as defined in claim 4 said means for adjusting the spacing between regions comprising an aperture through each region of said substrate, a tensioning member including a threaded portion at one extremity thereof extending through said aperture and having the other extremity thereof in pressure contact with one end of the folded assembly and threaded means riding on said threaded portion of said tensioning member for adjusting the tension between the ends of the said fan-fold assembly.
 6. An electromagnetic delay line as defined in claim 5 and wherein said tensioning member is of a material having magnetic properties.
 7. An electromagnetic delay line comprising: a thin flat elongated insulating substrate, a continuous conductor on one surface thereof forming a series of repetitive patterns, said substrate being adapted to be folded in alternate directions relative to the plane thereof along lines transverse to and spaced apart along the length of said substrate, said conductor forming a respective segment of the turn of a coil in each one of a set of successive regions along said substrate, each of said regions comprising the portion of said substrate between adjacent ones of said transverse lines, wherein all of said segments in each one of said sets form a complete coil turn, wherein all of said segments of said substrate form a multiturn coil, and a plurality of grounded areas on the other surface thereof.
 8. The electromagnetic delay line formed by folding the substrate of claim 7 in alternate directions relative to the plane thereof along said transverse lines.
 9. The electromagnetic delay line of claim 8 further including a first terminal connected to one end of said conductor, a second terminal connected to the other end of said conductor, and means for connecting to said grounded areas.
 10. An electromagnetic delay line as defined in claim 9 and including taps at predetermined turn positions of said coil.
 11. An electromagnetic delay line as defined in claim 9 including means for adjusting the spacing between adjacent regions of said substrate.
 12. An electromagnetic delay line as defined in claim 1 and wherein said tensioning member is of a material having magnetic properties.
 13. An electromagnetic delay line comprising a first nonconductive substrate, said substrate having a first repetitive plurality of conductive segments thereon forming a continuous conductor, a second nonconductive substrate having a second repetitive plurality of conductive areas thereon forming a continuous conductor, said second substrate being superimposed in suitable relationship on said first substrate, said first and second substrate being plicated in accordionlike fashion along selected plication lines, whereby said first plurality forms a multiturn coil of serially connected turns having at least first and Second terminals and said second plurality forms a set of parallel connected ground planes interleaved between said turns and insulated therefrom.
 14. An electromagnetic delay line comprising a nonconductive two-sided substrate, said substrate having a first repetitive plurality of conductive segments being serially connected forming a first continuous conductor on one side thereof and a second repetitive plurality of conductive areas being parallel connected forming a second continuous conductor on the other side thereof in predetermined relationship with said first conductor, said first and second conductors being insulated from one another by said substrate said substrate being plicated in accordionlike fashion along selected plication lines, whereby said first plurality forms a multiturn coil of serially connected turns having at least first and second terminals and said second plurality forms a set of parallel connected ground planes interleaved between said turns and insulated therefrom. 